I am pretty new with IronPort but i need to se up a relay on our internal interface on the Ironport and everyting is working great as long as I specify the SMTP-server with the IP-address instead of our dns entry which is mailrelay.doman.corp.
I can see that the traffic goes through our firewall nicely but it does not work. I does not see it in the messagetracking feature but if i simulate it in the Trace feauture it also works. It is a IronPort C370.
So to sum:
Mailrelay.domain.corp = 10.10.10.10
telnet 10.10.10.10 25 <-- This works
telnet Mailrelay.domain.corp 25 <-- This does Not work